bch_decode_berlekamp.m.txt

BCH码的Berklak-Massey算法

function errpos=BCH_decode_berlekamp(R,N,K,T)
  %received vector R
  % Caculate the S2t syndrome values.
  S=-1*ones(1,2*T);

  for i=1:2*T
    S(i)=GF_polyeval(R,i);
  end

  % Solving the system of equations using Berlekamp Massey Algorithm
  %disp("Syndrome Vector")
  S(1:2*T);
  S=[-1 S];
  one_Sx = [0 S(2:end)];

  iK=[0];        %Iteration Count?
  iLambda={0}; %Matrix of polynomials,
  iT={0};     %Matrix of polynomials,
  iDelta=[S(2)]; %Delta is coefficient of x^(2*K +1) in the polynomial


 % disp("Entering Evaluator........");

  for k=1:T
    %Lambda(2k+2)(x) = Lambda(2k)(x) + Delta(2k)*[x*T(2k)(x)]
    u=GF_product([-1 0],iT{k},iDelta(k));
    t=[ iLambda{k} -1*ones(1,length(u)-length(iLambda{k}))];
    v=-1*ones(1,length(t));

    for i=1:length(v)
      v(i)=GF_add(t(i),u(i));
    end
    iLambda{k+1}=v;

    %calculate T,
    if iDelta(k) == -1
      iT{k+1}= GF_product([-1 -1 0],iT{k});
    else
      v= GF_product([-1 0],iLambda{k});
      delinv=GF_complement(iDelta(k));
      u=-1*ones(1,length(v));

      for i=1:length(v)
	u(i)=GF_mul(v(i),delinv);
      end

      iT{k+1}=u;
    end
    iT{k+1};

    %Delta is coefficient of x^(2*K +1) in the polynomial product (Lambda_2k(X))*(1+S(x))
    %
    %    if (GF_polydegree(local_poly)<(2*k+2))
    %      iDelta(k)= -1;
    %    else

    %disp('Polynomial')
    one_Sx;
    iLambda{k+1};
    local_poly=GF_product(iLambda{k+1},one_Sx);
    iDelta(k+1)=local_poly(2*k+2); %Coefficient of x^2k+1 is located at index 2k+2

    %    fgets(stdin);
    %disp("Iteration ************************************************");

    %disp("Lambda(k+1)");
    %iLambda{k+1};

    %disp("T(k+1)");
    %iT{k+1};

    %disp("Delta(k+1)");
    %iDelta(k+1);
    % fgets(stdin)

  end

  iLambda{T+1};
  % Find the roots of Lambda

%  disp("Error Polynomial");
   ErrorPoly=iLambda{T+1};

% disp("Roots")
  errpos=GF_roots(ErrorPoly);

%  one_Sx;
%  iLambda;
%  iDelta;
%  iT;
%  iK;

  return
end